09-02-2013, 03:04 PM
TELOMERES & AGEING
TELOMERES.pptm (Size: 199.54 KB / Downloads: 37)
Telomeres are…
Repetitive DNA sequences at the ends of all human chromosomes
Contain thousands of repeats of the six-nucleotide sequence, TTAGGG
In humans there are 46 chromosomes and thus 92 telomeres (one at each end)
What do telomeres do?
Protect the chromosomes.
Separate one chromosome from another in the DNA sequence
Without telomeres, the ends of the chromosomes would be "repaired“.
Allow cell to differentiate between natural chromosome ends and damaged DNA.
Telomeres are also thought to be the "clock" that regulates how many times an individual cell can divide.
Structure of Telomeres
Telomere are composed of tandem repeats of GC rich
DNA sequence and telomere associated protein.
In human, the repeat is TTAGGG, up to 10,000bp in
Length.
Telomeres & Ageing
Once the telomere shrinks to a certain level, the cell can no longer divide. It’s metabolism slows down, it ages, and dies.
Healthy human cells are mortal because they can divide only a finite number of times, growing older each time they divide.
How Does Telomerase Work?
Research also shows that the counter that controls the wasting away of the telomere can be "turned on" and "turned off". The control button appears to be an enzyme called telomerase which can rejuvenate the telomere and allow the cell to divide endlessly.
Most cells of the body contain telomerase but it is in the "off" position so that the cell is mortal and eventually dies.